Picture a walk-in cooler that quits at 11 p.m. on a Friday. Nobody's in the building. By the time the morning crew opens the door, the product has been sitting warm for hours, and the only question left is how much of it goes in the dumpster.

That's the problem a temperature monitor solves. A thermometer tells you the temperature right now, while you're standing there looking at it. A monitor keeps watching after you walk away. Depending on the type, it remembers what happened, warns you when something goes wrong, or does both.

The main kinds of temperature monitors

Min/max thermometers are the simplest version. They show the current reading plus the highest and lowest temperatures since you last reset them. Check one each morning and you'll know whether the fridge drifted out of range overnight. You won't know when it happened or for how long, though.

Alarm thermometers add high and low setpoints. Go past either one and the unit beeps or flashes. That works well as long as someone is close enough to notice. The panel meters and probe units in our thermometers with alarms collection fall into this group.

Data loggers take a reading at a set interval, every minute or every fifteen, and store it for days or months. Afterward you download a time-stamped history. If an inspector, a customer or your own QA program wants proof that product stayed in range, a logger is usually the answer. We're a Master Distributor for LogTag, so these are a big part of what we do. Some LogTag models show a summary right on the display, some produce a PDF report when you plug them into a USB port, and some upload over Wi-Fi. Take a look at our LogTag recorders or the full data logger collection.

Wireless monitoring systems combine logging with remote alerts. Sensors report back to a base station or an online account, and you get a text or email when a reading goes out of range. That's the setup that would have saved the walk-in above.

Under the hood, most of these use a thermistor, a thermocouple or an RTD as the actual sensor. If you're curious how those differ, we cover it in Devices Used to Measure Temperature.

Who needs one

Any time product or equipment can be damaged by temperature and nobody is watching it around the clock, a monitor earns its keep. Restaurant coolers and freezers. Vaccine and medication storage. Labs, greenhouses, hatcheries, server rooms and refrigerated shipments. Some of these come with outside recordkeeping requirements. Others are just about not losing a load of product.

A few questions narrow it down fast:

• Do you need a record, or just a warning?
• Is anyone nearby to hear an alarm, or do alerts need to reach a phone?
• Are you measuring the air or the product? A probe sitting in a glycol bottle reads closer to product temperature than an air sensor does.
• Does it need a NIST traceable certificate? Many of our monitors and loggers offer one as an option.

Need to check or recalibrate monitors you already own? Our in-house lab can help. Start with the calibration and repair form, or call and ask for ext 3.

And if you're stuck between two options, just call us. We've been doing this since 1990, and we'd much rather spend five minutes on the phone than have you buy the wrong thing.